Radio frequency devices, such as resonant absorbers, acousto-magnetic structures and radio frequency identification (RFID) tags, can be encapsulated in mechanically robust materials, such as laminations of plastic or injection molded thermoplastic cases to protect them from either intentional or unintentional damage. One application of such devices is in electronic article surveillance (EAS) tags, which are commonly used in various locations to prevent unauthorized removal of inventory from a controlled area. Such tags may be paired with a detection system that is located at a boundary of the controlled area, and which generates an alert when an EAS tag is detected proximate to the detection system. For example, in retail establishments, EAS tags are affixed to articles for sale within the establishment and detection systems are installed at points of exit from the establishment. Thus, attempts at inventory theft are detected and successful attempts are markedly reduced.
Alternatively the movement of the devices may be tracked at locations inside a controlled area, such as a changing room in a apparel retail establishment, to detect unusual events that may be associated with theft occurring. To remove an article from a controlled area, the tag must be decoupled from the article. As tags are intended to only be decoupled from articles by personnel authorized to do so, special tools or detachment devices are typically provided so as to decouple the tag without damaging the article. Many such tools and detachment devices utilize solely mechanical means to detach the tag. However, such tags are susceptible to detachment by unauthorized individuals who can employ an approximation of the detachment mechanism to defeat the tag. Other types of EAS tags may utilize more sophisticated methods for detachment, for example non-mechanical or non-contact methods. However, such tags result in increased costs of manufacture and increased costs of utilization. Thus, a low-cost electronic article surveillance tag that is not easily defeatable by unauthorized methods is needed.